A magnetic disk unit includes a magnetic disk that rotates and a slider in which a magnetic recording/reproducing element included in a magnetic head is incorporated and which is borne by a suspension. The slider relatively travels over a magnetic disk, and the magnetic recording/reproducing element writes or reads magnetic information in or from the magnetic disk. The slider floats as an air lubrication bearing due to the wedge film effect of air, whereby the magnetic disk and slider do not come into solid contact with each other. In order to realize a magnetic disk unit featuring a high recording density and a large capacity stemming from the high recording density or a compact design, it would prove effective to reduce the distance between the magnetic recording/reproducing element and magnetic disk, that is, reduce a magnitude of floating of the slider, and increase a line recording density.
In the past, when a magnitude of floating of a slider is designed, a decrease in a magnitude of floating stemming from a difference caused by machining, a difference in an atmospheric pressure in a use environment, or a difference in temperature in the use environment has been estimated, and a margin of error in the magnitude of floating has been designated for fear that a slider and a disk may come into contact under the worst condition. If a slider having the ability to adjust a magnitude of floating for an individual head or according to a use environment is realized, the margin of error could be abolished. Consequently, while the contact between the slider and disk is prevented, the distance between a magnetic recording/reproducing element and the magnetic disk can be greatly decreased.
JP-A No. 20635/1993 (Patent Document 1) describes a technology for minimizing the gap between the distal ends of magnetic poles and the surface of a magnetic disk according to which: a thin-film resistor is interposed between a lower magnetic pole of an inductive thin-film magnetic head and an upper magnetic pole thereof, and heated if necessary by conducting electricity in order to project the distal ends of the magnetic poles through thermal expansion. JP-A No. 335069/2004 (Patent Document 2) describes a technology for making an amount of heat dissipated from a heating portion of a heater larger than an amount of heat dissipated from lead portions thereof by making a sheet resistance offered by the heading portion larger than a sheet resistance offered by the lead portions.
A heating portion and lead portions of a heater incorporated in a thin-film magnetic head are produced in the course of a thin-film formation process. In general, the heating portion is formed, and the lead portions are then formed so that one ends of the lead portions will overlap a conductor of the heating section. At this time, a contact resistance or any other resistance may be varied depending on a way of overlapping patterns. If the contact resistance increases at the overlaps between the conductor of the heating portion and the lead portions, a resistance offered by the lead portions increases. This causes a heat loss occurring at the lead portions to increase. Consequently, the heating portion fails to dissipate a predetermined amount of heat. This signifies that an expected effect of minimizing a magnitude of floating is not exerted. The foregoing existing technology does not take account of a change in the contact resistance attributable to the overlapping of patterns.